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use ArgdataRef;
use ReadError;
/// An iterator, iterating over an argdata map.
#[derive(Copy, Clone)]
pub struct MapIterator<'a, 'd: 'a> {
map: &'a (MapIterable<'d> + 'a),
cookie: usize,
}
/// Something that can be iterated over using a [`MapIterator`].
pub trait MapIterable<'d>: Sync {
/// Iterate to the next key-value pair, returning None if the end is reached.
///
/// **Don't use this method directly.**
/// Instead, get a [`MapIterator`] (using [`::Argdata::read_map`]), and
/// use it as any other [`Iterator`].
///
/// # For implementors
///
/// Use `cookie` to keep track of where the iterator is, and modify it in
/// this method to advance the iterator to the next element. The value of
/// the `cookie` is implementation-specific. It might for example be the
/// index into a vector, or the byte-offset into an encoded argdata value.
/// The initial value is also implementation specific, so provide a method
/// (such as [`Argdata.read_map`]) which provides users with a properly
/// initialized [`MapIterator`].
///
/// # Panics
///
/// May panic if you give it an invalid `cookie`.
fn iter_map_next<'a>(
&'a self,
cookie: &mut usize,
) -> Option<Result<(ArgdataRef<'a, 'd>, ArgdataRef<'a, 'd>), ReadError>>
where
'd: 'a;
}
impl<'a, 'd: 'a> MapIterator<'a, 'd> {
/// Create a new iterator.
///
/// This should only be used in implementations of [`MapIterable`].
///
/// To get a map iterator over Argdata use [`::Argdata::read_map`].
pub fn new(map: &'a (MapIterable<'d> + 'a), cookie: usize) -> Self {
MapIterator { map, cookie }
}
}
impl<'a, 'd: 'a> Iterator for MapIterator<'a, 'd> {
type Item = Result<(ArgdataRef<'a, 'd>, ArgdataRef<'a, 'd>), ReadError>;
fn next(&mut self) -> Option<Self::Item> {
self.map.iter_map_next(&mut self.cookie)
}
}
impl std::fmt::Debug for MapIterator<'_, '_> {
fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
write!(f, "MapIterator(.., {})", self.cookie)
}
}